Certain materials have a limited ductility. That is particularly the case with metals such as titan alloys or types of steel having a high limit of elasticity.
In this context, shaping of certain workpieces, especially tubular pieces, may be done by means of hydroforming machines, such as described in documents U.S. Pat. Nos. 6,305,204 4,557,128. In those machines, the fluid under pressure transits to the forming chamber through a channel having a small diameter provided in a cylindrical tool penetrating into the tube to be deformed.
Those hydroforming techniques ensure a progressive deformation of the material through obtaining provision of fluid under pressure by specific means.
But the deformation of the material obtained by such hydro-forming techniques generates an elastic return at the end of the process, which may appear limiting as far as applications are concerned.
In a very different field, which needs rather specific knowledge, forming of those materials may be done by high-velocity and high-pressure forming techniques, especially by electro-hydraulic forming techniques, or electro-hydroforming techniques, such as described in document EP-1 488 868.
Those electro-hydraulic forming techniques are based on the rapid movement of a forming fluid applied to one of the faces of the wall of the workpiece to be deformed, together with a rapid increase of the pressure of that fluid (contrarily to the progressive increase of pressure of hydroforming machines).
The forming fluid is then used as a means for stamping the piece to be deformed.
The energy that is necessary for the forming action is available as a shock wave in the forming fluid.
However, present electric hydroforming machines are not entirely adapted to apply certain deformations to specific structures of workpieces, especially an expansion to cylindrical tubular pieces having small diameters.